Passive thermal management system for battery

ABSTRACT

A battery module includes one or more battery cells and one or more laminated elements configured to provide passive management of heat generated by the one or more battery cells. Each laminated element includes one or more heat conducting layers and one or more intumescent layers. The one or more intumescent layers are configured to expand in response to an intumescent layer temperature exceedance to reconfigure the laminated element from a first configuration in which the laminated element transfers heat emitted by the one or more battery cells to a second configuration in which the laminated element does not substantially transfer heat emitted by the one or more battery cells.

BACKGROUND

Battery powered devices are becoming increasingly common. In manyapplications, the size and/or weight of the battery used to power thedevice is preferably as small as possible with respect to the powerrequired by the device. Additionally, it is preferable that the batteryhave a long life that accommodates a high number of discharge/chargecycles. For example, because lithium ion (Li-ion) batteries have a highspecific energy and have a favorable aging characteristics relative tolead acid batteries and nickel metal hydride batteries, Li-ion batteriesare in wide use in portable electronics (e.g., cell phones, portablecomputers, etc.). The use of Li-ion batteries in electric vehicles isalso increasing.

High specific energy batteries, however, may be susceptible tocatastrophic thermal runaway. Thermal runaway may be triggered viaconditions such as overcharge, over-discharge, and/or internal shortcircuits, which may cause an internal temperature of the battery tosignificantly exceed a safe temperature limit. Above a criticaltemperature, exothermic reactions can occur that cause furthertemperature increase, which may result in additional exothermicreactions leading to thermal runaway. A thermal runaway can be asignificant safety issue. For example, with a Li-ion battery,temperatures as high as 900° C. may occur as well as the release of asubstantial amount of flammable and toxic gas.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments in accordance with the present disclosure will bedescribed with reference to the drawings, in which:

FIG. 1 is a simplified cross-sectional schematic diagram illustrating abattery module that includes laminated elements configured to passivelymanage heat generated by battery cells, in accordance with manyembodiments;

FIG. 2 is a simplified cross-sectional schematic diagram illustratingone of the laminated elements of the battery module of FIG. 1;

FIG. 3 is a simplified cross-sectional schematic diagram illustrating abattery that includes the battery module of FIG. 1;

FIG. 4 is a simplified schematic diagram illustrating an electricvehicle that includes a battery module that includes laminated elementsconfigured to passively manage heat generated by battery cells, inaccordance with many embodiments;

FIG. 5 is a simplified schematic diagram illustrating an air vehiclepowered by a battery module that includes laminated elements configuredto passively manage heat generated by battery cells, in accordance withmany embodiments; and

FIG. 6 is a simplified schematic diagram illustrating a portableelectronic device powered by a battery module that includes laminatedelements configured to passively manage heat generated by battery cells,in accordance with many embodiments.

DETAILED DESCRIPTION

In the following description, various embodiments will be described. Forpurposes of explanation, specific configurations and details are setforth in order to provide a thorough understanding of the embodiments.However, it will also be apparent to one skilled in the art that theembodiments may be practiced without the specific details. Furthermore,well-known features may be omitted or simplified in order not to obscurethe embodiment being described.

Components, assemblies, and related approaches described hereinpassively accomplish thermal management in a battery. In manyembodiments, at least one laminated element is configured to: (1)conduct heat away from one or more battery cells during normaloperational conditions, and (2) reconfigure into a non-heat conductingconfiguration when exposed to temperatures indicative of thermal runawayof the one or more battery cells. By incorporating at least one of thelaminated elements into a battery module, heat generated by the batterymodule can be transferred from the one or more battery cells to exteriorto the battery module during normal operation without having to employactive cooling elements (e.g., fans, coolant pumps). Additionally,because the laminated element(s) reconfigures into a non-heattransferring configuration when exposed to temperatures indicative ofthermal runaway, the battery module can employ a lighter and/or lessexpensive exterior housing and still provide thermal isolation of theone or more battery cells in the event of thermal runaway.

Turning now to the drawing figures in which like reference numbers referto like elements in the various figures, FIG. 1 shows a battery module10 that is configured to passively manage heat generated by the batterymodule 10, in accordance with many embodiments. The battery module 10includes an array battery cells 12, an upper cell holder 14, a lowercell holder 16, a cathode 18, an anode 20, laminated elements 22, acathode intumescent coating 24 between the cathode 18 and the cathodesof the array of battery cells 12, an anode intumescent coating 26between the anode 20 and the anodes of the array of battery cells 12, anoptional expandable thermal felt insulation 28, and an optionalwax/phase change material 30. In the illustrated embodiment, the upperand lower cell holders 14, 16 have apertures through which ends of thearray of battery cells 12 extend and are held. The upper and lower cellholders 14, 16 can be made from any suitable material (e.g., polymeric,ceramic fiber board). The array of battery cells 12 extends throughapertures in the laminated elements 22, the expandable thermal feltinsulation 28, and, if included, through the wax/phase change material30. In embodiments, the wax/phase change material 30 is configured tomelt at a suitable temperature (e.g., 80 degrees Celsius).

The laminated elements 22 are initially configured to conduct heat awayfrom one or more battery cells during normal operational conditions.During normal operating conditions, heat generated by each cell of thearray of battery cells 12 is conducted away from cell by the laminatedelements 22. In the illustrated embodiment, the laminated elements 22contact each of the array of battery cells 12 and an external heat sink32 so as to provide a heat conduction path from the array of batterycells 12 to the heat sink 32. Any suitable external heat sink 32 can beused. For example, the battery module 10 can include athermally-conductive external housing that is thermally coupled with thelaminated elements 22 so that heat generated by the battery cells 12 istransferred to the housing for subsequent transmission external to thehousing.

The laminated elements 22 are further configured to reconfigure from theinitial heat-conducting configuration to a non-heat conductingconfiguration when exposed to high temperature generated by one or moreof the battery cells 12 during thermal runaway. As described herein indetail with reference to FIG. 2, each of the laminated elements 22includes heat conducting layers and intumescent layers that reconfigurewhen exposed to an elevated temperature thereby reconfiguring thelaminated element from the initial heat-conducting configuration to thenon-heat conducting configuration. When in the non-heat conductingconfiguration, the laminated element 22 is configured to inhibit heatconduction thereby helping to thermally isolate any cell of the array ofbattery cells 12 experiencing thermal runaway.

In some instances, the laminated elements 22 will locally reconfigurefrom the initial heat-conducting configuration to the non-heatconducting configuration. For example, when only one of the cells of thearray of battery cells 12 experiences a thermal runaway, a local portionof each of the laminated elements 22 adjacent to the where the laminatedelements 22 contact the cell experiencing thermal runaway canreconfigure into the non-heat conducting configuration thereby thermallyisolating the cell experiencing thermal runaway and stopping transfer ofheat to the remaining portion of the laminated element 22 still in theinitial heat-conducting configuration. Accordingly, the laminatedelements 22 may function to thermally isolate only cells experiencingthermal runaway while still conducting heat away from cells notexperiencing thermal runaway.

The cathode intumescent coating 24 between the cathode 18 and thecathodes of the array of battery cells 12 is initially configured toaccommodate electrical conduction between the cathode 18 and respectivecathodes of the array of battery cells 12. For example, in embodiments,contact areas of the respective cathodes of the battery cells 12 aremasked prior to application of the cathode intumescent coating 24 sothat the cathode 18 directly contacts the respective cathode contactareas. The cathode 18 can be made of any suitable electricallyconducting material (e.g., nickel, copper). Upon exposure to a suitabletemperature exceedance caused by a thermal runaway of one or more of thebattery cells 12, the cathode intumescent coating 24 expands to induceseparation between the cathode 18 and respective cathodes of batterycells of the array of battery cells 12 experiencing thermal runaway,thereby interrupting the electrical connection. Similar to theabove-described local expansion of the laminated elements 22, thecathode intumescent coating 24 may partially expand immediately adjacentto the cathodes of the battery cells 12 experiencing thermal runaway andthereby only disconnect the cathode 18 from the battery cells 12experiencing thermal runaway.

In a similar manner to the cathode intumescent coating 24, the anodeintumescent coating 26 between the anode 20 and the anodes of the arrayof battery cells 12 is initially configured to accommodate electricalconduction between the anode 20 and respective anodes of the array ofbattery cells 12. For example, in embodiments, contact areas of therespective anodes of the battery cells 12 are masked prior toapplication of the anode intumescent coating 26 so that the anode 20directly contacts the respective anode contact areas. The anode 20 canbe made of any suitable electrically conducting material (e.g., nickel,copper). Upon exposure to a suitable temperature exceedance caused by athermal runaway of one or more of the battery cells 12, the anodeintumescent coating 26 expands to induce separation between the anode 20and respective anodes of battery cells of the array of battery cells 12experiencing thermal runaway, thereby interrupting the electricalconnection. Similar to the above-described local expansion of thecathode intumescent coating 24, the anode intumescent coating 26 maypartially expand immediately adjacent to the anodes of the battery cells12 experiencing thermal runaway and thereby only disconnect the anode 20from the battery cells 12 experiencing thermal runaway.

FIG. 2 illustrates an embodiment of the laminated element 22. In theillustrated embodiment, the laminated element 22 includes intumescentlayers 34, support layers 36, and heat conducting layers 38. Theintumescent layers 34 are configured to expand when subjected to asuitable temperature (e.g., 200 to 300 degrees Celsius) induced as aresult of thermal runaway of one or more of the battery cells 12. Theintumescent layers 34 can be made from any suitable intumescentmaterial. For example, suitable intumescent materials include sodiumsilicate based materials, graphite based intumescent materials,carbon-rich polyhydric compounds with an acid release agent, amine oramide dehydration elements, and a blowing agent. The support layers 36can include any suitable material/elements (e.g., wire mesh, carbonmesh, felt) to provide support to the intumescent layers 34 and the heatconducting layers 38 during normal operating conditions in which nothermal runaway of the battery cells 12 occurs.

The heat conducting layers 38 can be made from any suitable materialthat can be reconfigured when exposed to a temperature exceedanceresulting from thermal runaway of one or more of the battery cells 12.For example, in embodiments, the heat conducting layers 38 include aheat conductive material (e.g., aluminum nitride, carbon black)suspended in a matrix material (e.g., a synthetic wax, polyethyleneterephthalate (PET), low-density polyethylene (LDPE)) having a suitablylow melting temperature (e.g., 80 to 120 degrees Celsius). During normaloperating conditions (i.e., no thermal runaway in any of the batterycells 12), the heat conducting layers 38 conduct heat away from thebattery cells (12). During thermal runaway of one or more of the batterycells 12, the matrix material melts first (e.g., at 80 to 120 degreesCelsius) thereby decreasing the heat conductivity of the heat conductinglayers 38 and providing an initial level of thermal isolation of the oneor more battery cells 12 experiencing thermal runaway.

With sufficient additional temperature exceedance (e.g., 200 to 300degrees Celsius), the intumescent layers 34 expand to further decreasethe heat conductivity of the heat conducting layers 38. The expansion ofthe intumescent layers 34 increases the insulating properties of thelaminated element 22, thereby increasing the thermal isolation of theone or more battery cells 12 experiencing thermal runaway.

Any suitable approach can be used to fabricate the laminated element 22.For example, the heat conducting layer 38 can be formed via melting androll forming or doctor blade. A laminated sheet can be formed thatincludes a heat conducting layer 38 and an intumescent layer 34. Forexample, an intumescent material can be sprayed onto a heat conductinglayer 38. The laminated sheet can also be formed by bonding a sheet ofintumescent material to a heat conducting layer 38 by elevating thetemperature of the sheets close to the melting temperature of the heatconducting layer 38 and pressing the sheets together (e.g., using aroller) to bond the intumescent layer 24 and the heat conducting layer38 together. The laminated element 22 can be formed by cutting andstacking the laminated sheets with alternating layers. The laminatedelement 22 can also be formed by spraying an intumescent material onto aheat conducting layer 38, adding another heat conducting layer 38 ontothe sprayed intumescent layer and repeating any suitable number of timesto incorporate the desired suitable number of heat conducting layers 38separated by sprayed intumescent layers 34. The laminated element 22 canalso be formed by positioning sheets of intumescent material in a toolwith standoffs and use closed tool forming to create large bi-materialsheets via injection. The large bi-material sheets can be trimmed and/orformed as desired using conventional machining approaches.Alternatively, the closed tool can be configured to form net shapelaminated elements with or without all the holes through which thebattery cells extend. One or more support layers 36 can be includedusing the same approaches.

The battery module 10 can be incorporated into any suitable battery. Forexample, FIG. 3 illustrates a battery 50 that includes the batterymodule 10. The battery 50 includes a thermally conductive housing 52enclosing the battery module 10, an exterior heat sink 54, and thermallyconductive stand-offs 56 thermally coupling the housing 52 to the heatsink 54. In the illustrated embodiment, the battery 50 further includesan optional exterior intumescent coating 58 configured to expand if thetemperature of the housing 52 exceeds a suitable temperature (e.g., 200to 300 degrees Celsius) to provide additional thermal isolation of thebattery 50 in addition to the passive thermal isolation provided in thebattery module 10 via the laminated elements 22, the cathode intumescentcoating 24, and the anode intumescent coating 26 as described herein.The exterior heat sink 54 can be placed in a location suitable todissipate heat from the exterior heat sink 54. For example, when thebattery 50 is used to power a vehicle, the heat sink 54 can be locatedat an exterior surface of the vehicle to transfer heat from the heatsink 54 to the surrounding ambient environment.

The battery 50 can be used to power any suitable electrically powereditem. For example, FIG. 4 is a simplified schematic diagram illustratingan electric car 60 that includes the battery module 50. The electric car60 further includes an electric motor 62 that powers drive wheels 64 viaa transmission 66. As described herein, the heat sink 54 of the battery50 can be located at an external surface of the electric car 60 totransfer heat from the heat sink 54 to the surrounding environmentduring normal operating conditions. As another example, FIG. 5 is asimplified schematic diagram illustrating a remotely controlled drone 70that includes the battery module 50. The drone 70 further includeselectric motors 72 that power rotors 74. As described herein, the heatsink 54 of the battery 50 can be located at an external surface of thedrone 70 to transfer heat from the heat sink 54 to the surroundingenvironment during normal operating conditions. As yet another example,FIG. 6 is a simplified schematic diagram illustrating an electronicdevice 80 that includes the battery 50. The electronic device 80 furtherincludes one or more electrically powered components 82 powered by thebattery 50. The electronic device 80 can be any suitable poweredportable electronic device (e.g., laptop computer, cellular phone,fitness monitoring device, tablet, electronic book).

The specification and drawings are, accordingly, to be regarded in anillustrative rather than a restrictive sense. It will, however, beevident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the disclosure asset forth in the claims.

Other variations are within the spirit of the present disclosure. Thus,while the disclosed techniques are susceptible to various modificationsand alternative constructions, certain illustrated embodiments thereofare shown in the drawings and have been described above in detail. Itshould be understood, however, that there is no intention to limit thedisclosure to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the disclosure,as defined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosed embodiments (especially in thecontext of the following claims) are to be construed to cover both thesingular and the plural, unless otherwise indicated herein or clearlycontradicted by context. The terms “comprising,” “having,” “including,”and “containing” are to be construed as open-ended terms (i.e., meaning“including, but not limited to,”) unless otherwise noted. The term“connected” is to be construed as partly or wholly contained within,attached to, or joined together, even if there is something intervening.Recitation of ranges of values herein are merely intended to serve as ashorthand method of referring individually to each separate valuefalling within the range, unless otherwise indicated herein and eachseparate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate embodiments of the disclosure anddoes not pose a limitation on the scope of the disclosure unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe disclosure.

Disjunctive language such as the phrase “at least one of X, Y, or Z,”unless specifically stated otherwise, is intended to be understoodwithin the context as used in general to present that an item, term,etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y,and/or Z). Thus, such disjunctive language is not generally intended to,and should not, imply that certain embodiments require at least one ofX, at least one of Y, or at least one of Z to each be present.

Preferred embodiments of this disclosure are described herein, includingthe best mode known to the inventors for carrying out the disclosure.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate and the inventors intend for the disclosure to be practicedotherwise than as specifically described herein. Accordingly, thisdisclosure includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the disclosure unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

What is claimed is:
 1. A battery module comprising: an array of batterycells; a cell holder supporting the array of battery cells; and alaminated element contacted with each of the battery cells, thelaminated element including heat conducting layers and intumescentlayers interspersed with the heat conducting layers, the intumescentlayers being configured to expand in response to an intumescent layertemperature exceedance to reconfigure the laminated element from a firstconfiguration in which the laminated element transfers heat emitted bythe array of battery cells to a second configuration in which thelaminated element does not substantially transfer heat emitted by thearray of battery cells.
 2. The battery module of claim 1, wherein eachof the heat conducting layers includes a heat conductive materialsuspended in a matrix material, the matrix material having a meltingpoint temperature in a range from 80 to 120 degrees Celsius.
 3. Thebattery module of claim 1, further comprising: an anode intumescentlayer configured to expand in response to an anode intumescent layertemperature exceedance to reconfigure the anode intumescent layer from afirst configuration in which the anode intumescent layer permits currentflow via anodes of the array of battery cells to a second configurationin which current flow via at least one anode of the array of batterycells is at least partially inhibited relative to current flow in thefirst configuration; and a cathode intumescent layer configured toexpand in response to a cathode intumescent temperature exceedance toreconfigure the cathode intumescent layer from a first configuration inwhich the cathode intumescent layer permits current flow via cathodes ofthe array of battery cells to a second configuration in which currentflow via at least one of the array of battery cells is at leastpartially inhibited relative to current flow in the first configuration.4. A battery module comprising: a first battery cell; and a laminatedelement including one or more heat conducting layers and one or moreintumescent layers, the one or more intumescent layers being configuredto expand in response to an intumescent layer temperature exceedance toreconfigure the laminated element from a first configuration in whichthe laminated element transfers heat emitted by the first battery cellto a second configuration in which the laminated element does notsubstantially transfer heat emitted by the first battery cell.
 5. Thebattery module of claim 4, wherein at least one of the one or more heatconducting layers reconfigures from a heat-conducting configuration to anon-heat-conducting configuration in response to a heat conducting layertemperature exceedance, the heat-conducting configuration transferringheat emitted by the first battery cell, and the non-heat-conductingconfiguration not substantially transferring heat emitted by the firstbattery cell.
 6. The battery module of claim 5, wherein at least one ofthe one or more heat conducting layers includes a heat conductivematerial suspended in a matrix material that melts in response to theheat conducting layer temperature exceedance.
 7. The battery module ofclaim 6, wherein the heat conducting layer temperature exceedanceincludes a temperature increase above a temperature in a range from 80to 120 degrees Celsius.
 8. The battery module of claim 6, wherein: thematrix material includes a synthetic wax; and the heat conductivematerial includes at least one of aluminum nitride or carbon black. 9.The battery module of claim 4, wherein the intumescent layer temperatureexceedance includes a temperature increase above a temperature in arange from 200 to 300 degrees Celsius.
 10. The battery module of claim4, wherein the first battery cell has a first battery cell anode and afirst battery cell cathode, the battery module further comprising atleast one of: an anode intumescent layer configured to expand inresponse to an anode intumescent layer temperature exceedance toreconfigure the anode intumescent layer from a first configuration inwhich the anode intumescent layer permits current flow via the firstbattery cell anode to a second configuration in which current flow viathe first battery cell anode is at least partially inhibited relative tocurrent flow in the first configuration; or a cathode intumescent layerconfigured to expand in response to a cathode intumescent temperatureexceedance to reconfigure the cathode intumescent layer from a firstconfiguration in which the cathode intumescent layer permits currentflow via the first battery cell cathode to a second configuration inwhich current flow via the first battery cell cathode is at leastpartially inhibited relative to current flow in the first configuration.11. The battery module of claim 4, further comprising a second batterycell, and wherein the laminated element is configured to transfer heatemitted by the second battery cell when the laminated element is in thefirst configuration and does not substantially transfer heat emitted bythe second battery cell when the laminated element is in the secondconfiguration.
 12. The battery module of claim 11, wherein each of thefirst and second battery cells extends at least partially through arespective aperture through the laminated element.
 13. The batterymodule of claim 12, further comprising a second laminated element, andwherein each of the first and second battery cells extends at leastpartially through a respective aperture through the second laminatedelement.
 14. The battery module of claim 4, wherein the laminatedelement includes a plurality of laminated subassemblies, each of thelaminated subassemblies including one of the heat conducting layers andone of the intumescent layers.
 15. The battery module of claim 14,wherein at least one of the laminated subassemblies includes a supportlayer that includes at least one of a wire mesh or a carbon mesh. 16.The battery module of claim 4, further comprising a thermally conductivehousing enclosing the first battery cell and the laminated element, thethermally conductive housing being coupled with the laminated elementwhen the laminated element is in the first configuration to transferheat from the laminated element.
 17. The battery module of claim 16,further comprising a heat sink element thermally coupled with thethermally conductive housing via one or more thermally conductivestandoff members.
 18. A laminated structure for passive management ofheat generated by a battery, the laminated structure comprising one ormore heat conductive layers and one or more intumescent layersinterspersed with the one or more heat conductive layers, each of theone or more intumescent layers being configured to expand in response toan intumescent layer temperature exceedance to reconfigure the laminatedstructure from a first configuration in which the laminated structure isheat conductive to a second configuration in which the laminatedstructure is not substantially heat conductive.
 19. The laminatedstructure of claim 18, further comprising one or more support layersinterspersed with the one or more heat conductive layers and the one ormore intumescent layers, each of the support layers comprising areinforcing mesh.
 20. The laminated structure of claim 18, wherein atleast one of the one or more heat conducting layers reconfigures from aheat-conducting configuration to a non-heat-conducting configuration inresponse to a heat conducting layer temperature exceedance, theheat-conducting configuration transferring heat emitted by the firstbattery cell, and the non-heat-conducting configuration notsubstantially transferring heat emitted by the first battery cell.